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First PS-to-SPS Transfer MD

First PS-to-SPS Transfer MD. Helga Timkó BE-RF-BR in collaboration with Theodoros Argyropoulos , Thomas Bohl , Heiko Damerau , Steven Hancock, Juan Esteban Müller, Elena Shaposhnikova. Outline. Reminder of simulation results Report on the MD of 29 th March 2012

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First PS-to-SPS Transfer MD

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  1. First PS-to-SPS Transfer MD Helga Timkó BE-RF-BR in collaborationwith Theodoros Argyropoulos, Thomas Bohl, Heiko Damerau, Steven Hancock, Juan Esteban Müller, Elena Shaposhnikova

  2. Outline • Reminder of simulation results • Report on the MD of 29th March 2012 • Aim: Optimise the PS bunch rotation timings • Measurement conditions • Results and preliminary conclusions • Why further MDs are needed SPSU-BD Meeting

  3. PS-TO-SPS TRANSFER: WHAT SIMULATIONS PREDICT

  4. Optimising the PSbunch rotation timings • For 1+2 cavities, optimal timing reduces losses: 4.4 %  3.5 % • Using 2+3 cavities instead of 1+2: 3.5 %  1.3 % Transmission can be improved even w/o more voltage SPSU-BD Meeting

  5. Optimised bunch shapes … now improved: tails less populated SPSU-BD Meeting

  6. PS-TO-SPS TRANSFER: WHAT WE MEASURE

  7. Measurement conditions • Single batch, 25 ns spaced LHC-type beam, 72 bunches • Nominal intensity, 1.1  1011 ppb • In the PS: voltage programme as ‘usual’ • Varying the rotation timings t40 MHz and t80 MHz • In the SPS: FB voltage was 2 MV at injection, then immediately increased to 3 MV (“usual” procedure) • V800 MHz = 0.35 MV In bunch-shortening mode • Bunch length: measured at ejection from the PS with BSM • Cross-checked with bunch length measured at SPS injection • Transmission: logged from “LARGER” at the end of the FB (26 GeV) and at 62 GeV • Cross-checked with BCT data SPSU-BD Meeting

  8. Transmission • The transmission at 62 GeV is the relevant quantity for us, since it includes losses from the acceleration ramp SPSU-BD Meeting

  9. Transmission & bunch length • Better transmission can sometimes require longer bunches Optimum predicted by simulations Currently operational SPSU-BD Meeting

  10. Comparison with simulations • Systematically shorter bunches in this MD than earlier • In (b), we could fit the simulated curve, but also a constant • In (b), higher transmission for t40 MHz = 150 μs than expected • Measurement needs to be repeated Unexpectedly high transmission SPSU-BD Meeting

  11. Comparison with simulations • Simulations predict a maximum ~ t40 MHz = 170-190 μs, t80 MHz = 120 μs • Note: longer bunches, since we took the distributions of a previous MD • Effect is small with the current intensities (order of error bars); need very accurate measurements to verify this SPSU-BD Meeting

  12. Conclusions • The first measurements are encouraging • At least, they don’t contradict the simulations • No conclusive results yet • However, measurements are ‘tricky’ • We’re looking at percent-level differences • We have only percent-level accuracy • Need extremely stable beam conditions and need to ensure that the losses in the transverse plane are constant • Further measurements are planned for the future • Repeat the above & do the same scan with higher voltage SPSU-BD Meeting

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